1. Field of the Invention
This invention generally relates to processes for improving enzymatic degumming of vegetable oils. The process reduces fouling in post-reaction equipment. The invention is especially suitable for use in production lines within which edible oil is treated to prepare edible oil of salad oil quality. More particularly, the invention relates to process enhancements that create conditions in the oil being processed for minimizing build-up on equipment through which the thus treated oil passes.
2. Description of Related Art
Vegetable-based edible oils long have been processed into salad oils. A principal procedure in such processing is the so-called caustic process. In such a process, crude vegetable oil may or may not be filtered and may or may not be acid or water degummed. The filtration of crude oil is only utilized when “clear and brilliant” food grade lecithin is produced from a water degumming process. Degumming of crude oil with the aid of an acid, burns the lecithin yielding a product that is not desirable. In the water degumming process, crude oil is combined with water and degummed crude is prepared, with gums being removed and collected as desired. Water degumming can remove about two-thirds of the gums present in the crude oil. Typically, phosphoric acid is injected into the degummed crude, followed by sodium hydroxide in order to provide caustic treated oil, with soapstock being removed and collected as desired. Next, silica is added to the caustic treated oil, and spent silica is removed. Bleaching earth then is added to the silica treated oil to provide bleached oil, spent clay being removed. Then water is added to the bleached oil in a deodorizing process, with a distillate being separated. A drawback of such caustic processes is relatively low yields, plus the multiple steps that are followed to achieve desired salad oil quality oil.
The role of phosphoric acid is to treat the lecithin components in the oil. This process includes an add-back neutralization of the phosphoric acid which is needed to neutralize free fatty acids, yielding sodium soaps which separate out. It is recognized that taking an approach different from caustic oil refining could have advantages in the oil processing industry.
Approaches have been proposed whereby edible oil products are processed into salad oil products by an enzymatic approach during which fatty acids remain in the oil rather than following the separation approach of caustic refining, and the fatty acid content is transformed and stays in the vegetable oil until it is separated, such as by centrifugation.
In the oil refining art, references such as Aalrust et al. U.S. Pat. No. 5,264,367, incorporated by reference hereinto, teach enzymatic treatment of edible oils. In such approaches, phosphorus-containing components of an edible vegetable or animal oil that has been wet refined are reduced by enzymatic decomposition by contacting the oil with an aqueous solution of phospholipases A1, A2 or B and then separating the aqueous phase from the treated oil. This is said to reduce the phosphorus level in the oil to a substantial degree. While enzymatic treatment processes show good potential, the present invention achieves improvements over these processes. This invention provides means for improving oil degumming processes.
The present invention provides a novel type of process which facilitates the use of enzymes in edible oil refining, including degumming operations. The invention incorporates a post-reaction addition to reduce fouling. More specifically, anti-fouling component is added promptly downstream of the enzyme reactor. The anti-fouling component imparts enhanced processing properties to the degummed oil.
The art of enzymatic degumming has developed to provide, for example, the ability to hydrate selected cleavage sites of a lecithin or fatty acid natural oil component which needs to be degummed. Those enzymes having an A1 characteristic cleave the A1 site of the triglyceride molecule, enzymes having an A2 characteristic cleave at the A2 or B, or middle site, and those of a C characteristic cleave at the A3 site, which in these types of triglycerides have the undesirable phosphorus atom.
Heretofore, it has not been appreciated that enzymatic degumming operations of this type bring with them an undesirable build-up of residue on blades and other working surfaces of downstream equipment such as heat exchangers and centrifuge equipment. The combination of a post-reactor addition of an anti-fouling component and the enzymatic refining approach result, according to the invention, in high yield and smooth operating industrial-scale edible oil processing plants.